1. Field of the Invention
This invention relates to a light emitting device that a light emitting element is glass-sealed on a mounting board.
2. Description of the Related Art
A light emitting device (WO2004/082036) is proposed by the inventors et al. where a light emitting element such as a light emitting diode (LED) is used as a light source, and the light emitting element is glass-sealed by bonding a plate glass to a mounting board with the light emitting element mounted thereon by hot pressing. In the light emitting device (WO2004/082036), the light emitting element is flip-chip mounted on the mounting board. This is because face-up mounting requiring wire bonding is difficult to keep electrical connection since deformation of wire may be caused by high temperature and viscosity of glass during hot pressing.
JP-A-2006-156668 discloses a light emitting device that n-side electrode and p-side electrode of a light emitting element are bonded via a bump to an electrode on a mounting board. JP-A-2006-156668 teaches to use the bump that is formed of a metal such as Ag or its alloy to prevent short circuit caused by being softened due to heated and softened glass.
However, JP-A-2006-156668 has the problem that light emitted toward the mounting board is inputted to a metal surface of a wiring layer etc. formed on the light emitting element or the mounting board and metal reflection absorption loss is generated when light is reflected thereon. Therefore, light extraction efficiency lowers by the light loss. Especially, in case of flip-chip mounting, the size of a p-side pad electrode is increased to secure the electrical connection and, therefore, metal reflection absorption loss or light loss is also generated at the p-side pad electrode when light emitted from the light emitting element is inputted to the p-side pad electrode.